The discovery marks the greatest confirmed distance ever recorded between sightings of individual humpback whales anywhere in the world.

"Discoveries like this are only possible because of investment into long-term multi-decadal research programs and international collaboration," Griffith University Phd Candidate and co-author Stephanie Stack said.

"These whales were photographed decades apart, by different people, in opposite parts of the world, separated by two different oceans, and yet we can connect their journey."

Whale Tail Photos Reveal Record Journeys

Researchers identified the whales by comparing tens of thousands of photographs of humpback whale tails, known as flukes. Each whale has unique markings that allow scientists to recognize individuals over time.

One whale was first photographed in Hervey Bay, Queensland, in 2007. It was seen again in the same area in 2013 before later appearing near São Paulo, Brazil, in 2019.

The minimum straight-line distance between those breeding grounds is about 14,200 kilometers, roughly equivalent to the distance from Sydney to London.

Scientists noted that the whale likely traveled even farther because only the beginning and ending points of the journey were recorded. The exact migration route remains unknown.

A second whale produced an even more remarkable result. Researchers first photographed it in 2003 at Brazil's Abrolhos Bank, the country's main humpback whale nursery off the coast of Bahia. At the time, it was swimming in a lively group of nine adult whales.

Twenty-two years later, in September 2025, the same whale was spotted alone in Hervey Bay, Australia. The documented distance between sightings was 15,100 kilometers, setting a new record for the longest known movement of an individual humpback whale.

Decades of Research and Citizen Science

The study relied on 19,283 high-quality fluke photographs collected between 1984 and 2025 from eastern Australia and Latin America. The images came from both professional researchers and citizen scientists through the global whale tracking platform Happywhale.

Scientists used automated image recognition software to compare the photographs and then manually checked every possible match to confirm the findings.

"This kind of research highlights the value of citizen science," said lead researcher Dr. Cristina Castro from Pacific Whale Foundation.

"Every photo contributes to our understanding of whale biology and, in this case, helped uncover one of the most extreme movements ever recorded."

Despite the stunning distances involved, researchers emphasized how uncommon these migrations appear to be. Across more than four decades of data covering nearly 20,000 identified humpback whales, only two whales were found to have traveled between the two breeding regions. That represents just 0.01 percent of the whales included in the records.

Why Rare Whale Crossings Matter

Scientists say even these rare movements could play an important role in the long-term survival of whale populations.

"Despite their rarity, these exchanges matter for the long-term health of whale populations," Ms. Stack said.

"Occasional individuals moving between distant breeding grounds can help maintain genetic diversity across populations and may even carry new song styles from one region to another -- humpback whale songs are known to spread culturally across ocean basins, much like music trends in human populations."

The findings also support what researchers call the "Southern Ocean Exchange" hypothesis. This idea suggests that humpback whales from different breeding populations may occasionally meet in shared Antarctic feeding areas. Some whales may then return along a different migration route, eventually settling in a completely new breeding region.

Researchers believe climate change could make these rare crossings more common in the future. Shifts in Antarctic sea ice and changes in the distribution of Antarctic krill (the whales' primary food source) may be altering whale migration patterns over time.

The study, "First evidence of bidirectional exchange between distant humpback whale breeding populations in eastern Australia and Brazil," was published in Royal Society Open Science.